feat: add API to generate FB custom token from Kakao

cmd/server/handler/auth_handler.go

@@ -78,3 +78,42 @@ func (h *authHandler) KakaoCallback(w http.ResponseWriter, r *http.Request) {
 		PhotoURL:             userProfile.Properties.ProfileImage,
 	})
 }
+
+// GenerateFBCustomTokenFromKakao godoc
+// @Summary Kakao OAuth 토큰 기반 Firebase Custom Token 생성 API
+// @Description 주어진 카카오 토큰으로 사용자 기본 정보를 검증하고 Firebase Custom Token을 발급합니다.
+// @Tags auth
+// @Accept json
+// @Produce json
+// @Param request body auth.GenerateFBCustomTokenRequest true "Firebase Custom Token 생성 요청"
+// @Success 201 {object} auth.GenerateFBCustomTokenResponse
+// @Failure 400 {object} commonviews.ErrorView
+// @Router /auth/custom-tokens/kakao [post]
+func (h *authHandler) GenerateFBCustomTokenFromKakao(w http.ResponseWriter, r *http.Request) {
+	var tokenRequest auth.GenerateFBCustomTokenRequest
+	if err := commonviews.ParseBody(w, r, &tokenRequest); err != nil {
+		return
+	}
+
+	userProfile, err := h.kakaoClient.FetchUserProfile(tokenRequest.OAuthToken)
+	if err != nil {
+		commonviews.BadRequest(w, nil, "유효하지 않은 Kakao 인증 정보입니다.")
+		return
+	}
+
+	customToken, err := h.authService.CustomToken(r.Context(), fmt.Sprintf("%d", userProfile.ID))
+	if err != nil {
+		commonviews.InternalServerError(w, nil, err.Error())
+		return
+	}
+
+	w.Header().Set("Content-Type", "application/json")
+	w.WriteHeader(http.StatusCreated)
+	json.NewEncoder(w).Encode(auth.GenerateFBCustomTokenResponse{
+		AuthToken:            customToken,
+		FirebaseProviderType: user.FirebaseProviderTypeKakao,
+		FirebaseUID:          fmt.Sprintf("%d", userProfile.ID),
+		Email:                userProfile.KakaoAccount.Email,
+		PhotoURL:             userProfile.Properties.ProfileImage,
+	})
+}

cmd/server/main.go

@@ -11,7 +11,7 @@ import (
 )
 
 // @title 이웃집멍냥 API 문서
-// @version 0.7.0
+// @version 0.8.0
 // @description 이웃집멍냥 백엔드 API 문서입니다.
 // @termsOfService http://swagger.io/terms/
 

cmd/server/router.go

@@ -98,6 +98,7 @@ func NewRouter(app *firebaseinfra.FirebaseApp) *chi.Mux {
 		r.Route("/auth", func(r chi.Router) {
 			r.Get("/login/kakao", authHandler.KakaoLogin)
 			r.Get("/callback/kakao", authHandler.KakaoCallback)
+			r.Post("/custom-tokens/kakao", authHandler.GenerateFBCustomTokenFromKakao)
 		})
 		r.Route("/media", func(r chi.Router) {
 			r.Get("/{id}", mediaHandler.FindMediaByID)

internal/domain/auth/view.go

@@ -9,3 +9,19 @@ type KakaoCallbackResponse struct {
 	Email                string                    `json:"email"`
 	PhotoURL             string                    `json:"photoURL"`
 }
+
+// GenerateFBCustomTokenRequest는 OAuth 토큰 정보를 기반으로 Firebase Custom Token을 생성하기 위한 요청이다.
+type GenerateFBCustomTokenRequest struct {
+	OAuthToken string `json:"oauthToken"`
+	OAuthID    string `json:"oauthId"`
+	OAuthEmail string `json:"oauthEmail"`
+}
+
+// GenerateFBCustomTokenResponse는 Firebase Custom Token을 생성하기 위한 응답이다.
+type GenerateFBCustomTokenResponse struct {
+	AuthToken            string                    `json:"authToken"`
+	FirebaseProviderType user.FirebaseProviderType `json:"fbProviderType"`
+	FirebaseUID          string                    `json:"fbUid"`
+	Email                string                    `json:"email"`
+	PhotoURL             string                    `json:"photoURL"`
+}

internal/infra/kakao/client.go

@@ -2,6 +2,7 @@ package kakaoinfra
 
 import (
 	"encoding/json"
+	"fmt"
 	"io"
 	"net/http"
 	"strings"
@@ -70,7 +71,7 @@ func (kakaoClient *KakaoClient) FetchUserProfile(code string) (*kakaoUserProfile
 	}
 
 	if res.StatusCode != http.StatusOK {
-		return nil, err
+		return nil, fmt.Errorf("failed to fetch user profile from Kakao server")
 	}
 
 	body, err := io.ReadAll(res.Body)

pkg/docs/swagger.json

@@ -12,7 +12,7 @@
             "name": "Apache 2.0",
             "url": "http://www.apache.org/licenses/LICENSE-2.0.html"
         },
-        "version": "0.7.0"
+        "version": "0.8.0"
     },
     "basePath": "/api",
     "paths": {
@@ -33,6 +33,46 @@
                 }
             }
         },
+        "/auth/custom-tokens/kakao": {
+            "post": {
+                "description": "주어진 카카오 토큰으로 사용자 기본 정보를 검증하고 Firebase Custom Token을 발급합니다.",
+                "consumes": [
+                    "application/json"
+                ],
+                "produces": [
+                    "application/json"
+                ],
+                "tags": [
+                    "auth"
+                ],
+                "summary": "Kakao OAuth 토큰 기반 Firebase Custom Token 생성 API",
+                "parameters": [
+                    {
+                        "description": "Firebase Custom Token 생성 요청",
+                        "name": "request",
+                        "in": "body",
+                        "required": true,
+                        "schema": {
+                            "$ref": "#/definitions/auth.GenerateFBCustomTokenRequest"
+                        }
+                    }
+                ],
+                "responses": {
+                    "201": {
+                        "description": "Created",
+                        "schema": {
+                            "$ref": "#/definitions/auth.GenerateFBCustomTokenResponse"
+                        }
+                    },
+                    "400": {
+                        "description": "Bad Request",
+                        "schema": {
+                            "$ref": "#/definitions/commonviews.ErrorView"
+                        }
+                    }
+                }
+            }
+        },
         "/auth/login/kakao": {
             "get": {
                 "tags": [
@@ -596,6 +636,40 @@
         }
     },
     "definitions": {
+        "auth.GenerateFBCustomTokenRequest": {
+            "type": "object",
+            "properties": {
+                "oauthEmail": {
+                    "type": "string"
+                },
+                "oauthId": {
+                    "type": "string"
+                },
+                "oauthToken": {
+                    "type": "string"
+                }
+            }
+        },
+        "auth.GenerateFBCustomTokenResponse": {
+            "type": "object",
+            "properties": {
+                "authToken": {
+                    "type": "string"
+                },
+                "email": {
+                    "type": "string"
+                },
+                "fbProviderType": {
+                    "$ref": "#/definitions/user.FirebaseProviderType"
+                },
+                "fbUid": {
+                    "type": "string"
+                },
+                "photoURL": {
+                    "type": "string"
+                }
+            }
+        },
         "auth.KakaoCallbackResponse": {
             "type": "object",
             "properties": {
@@ -616,6 +690,14 @@
                 }
             }
         },
+        "commonviews.ErrorView": {
+            "type": "object",
+            "properties": {
+                "message": {
+                    "type": "string"
+                }
+            }
+        },
         "commonviews.PaginatedView-pet_BreedView": {
             "type": "object",
             "properties": {
@@ -1258,8 +1340,7 @@
                 "fbProviderType",
                 "fbUid",
                 "fullname",
-                "nickname",
-                "profileImageId"
+                "nickname"
             ],
             "properties": {
                 "email": {